Herein are described transient or temporary documents suitable for use in electrostatographic or electrophotographic printing or copying processes. More specifically, herein are described coated transient documents used in electrostatographic or electrophotographic recording processes, including electrostatography, electrophotography, xerography, ionography, digital, and the like, the transient documents are prepared by a solvent-less coating process. This process for coating transient documents dispenses with the need for solvents, which, when used, can be costly and dangerous to the environment. The current solvent-less process involves dissolving photochromic compounds in melted polymer or resin materials, and coating the recording material with the melted composition. In embodiments, the photochromic compounds are spiropyrans.
Transient documents are reimageable recording mediums, wherein the recording medium is capable of exhibiting a color contrast and an absence of color contrast. More specifically, a) the transient document is exposed to an imaging light corresponding to a predetermined image to result in an exposed region and a non-exposed region, wherein the color contrast is present between the exposed region and the non-exposed region to allow a temporary image corresponding to the predetermined image to be visible for a visible time. Next, b) the temporary image is subjected to an indoor ambient condition for an image erasing time to change the color contrast to the absence of the color contrast to erase the temporary image without using an image erasure device. Optionally, procedures a) and b) can be repeated a number of times to result in the medium undergoing a number of additional cycles of temporary image formation and temporary image erasure.
Disclosures of transient documents include the following.
Sebastian V. Kanakkanatt, “Photoerasing Paper and Thermocoloring Film,” SPIE, Vol. 3227, pp. 218-224 (1997).
Henri Bouas-Laurent et al., “Organic Photochromism,” Pure Appl. Chem., Vol. 73, No. 4, pp. 639-665 (2001).
Martin et al., U.S. Pat. No. 5,710,420.
McCue et al., U.S. Pat. No. 6,500,245 B1.
Japanese Patent Document Laid Open No. 2003-131339 (“Reversible Image Display Medium, Method and Device”).
I. Kawashima et al., “20.4: Photon-Mode Full-Color Rewritable Image Using Photochromic Compounds,” SID 03 DIGEST, pp. 851-853 (2003).
H. Hattori et al., “Development of Paper-like Rewritable Recording Media and Systems,” Asia Display/IDW '01, pp. 15-18 (2001).
Saeva, U.S. Pat. No. 3,961,948.
Foucher, et al., U.S. Pat. No. 6,358,655 B1.
Foucher et al., U.S. Pat. No. 6,365,312 B1.
Known processes for preparing recording mediums, which are not considered transient documents, include the use of solvents along with spiropyrans.
For example, U.S. Pat. No. 6,635,602 discloses use of organic solvents and fluoran compounds in a process for making recording materials. The patent discloses that spiropyrans can be added to the fluorans as color forming compounds in the paper itself.
U.S. Pat. No. 6,077,642 discloses use of a spiropyran as an electron donating dye in the process of making a recording material.
U.S. Pat. No. 5,803,505 discloses use of spiropyrans as color formers in a process for making a recording material having a multi-color imageable surface. The color formers comprise from about 5 to about 15 percent by weight of the coating composition.
U.S. Pat. No. 5,565,276 discloses a method for making anti-falsification paper using spiropyran as a fluorescent dye.
U.S. Pat. No. 5,524,934 discloses use of spiropyrans as color formers in a process for making a recording material having a multi-color imageable surface. The color formers comprise from about 5 to about 15 percent by weight of the coating composition.
U.S. Pat. No. 5,372,917 teaches use of spiro-based dyes and 3-methylnaphtho(6′-methoxybenzo)spiropyran in the process for making a recording material.
U.S. Pat. No. 5,312,686 discloses use of a spiropyran in the formation of recording materials.
U.S. Pat. No. 5,300,661 discloses use of a fluoran compound and possible spiropyran in order to adjust the developed hue in a process for making a recording material.
A need remains for an improved process for producing transient documents, which dispenses with the need for solvents, and produces a transient document that has performance equivalent to the transient documents produced by known solvent-based methods. Solvents, when used, can be costly and dangerous to the environment. Solvent containment is needed in known methods in order to avoid release of solvents into the atmosphere. The present solvent-less process dispenses with the need for solvent containment. In addition, solvents are flammable, and there is a risk of fire during the fabrication process. With the current solvent-less process, this risk is eliminated. Moreover, using solvents requires the need for heating in order to fully evaporate the remaining solvent. Incomplete evaporation of the solvent may leave the smell of residual solvent on the transient document. The current solvent-less process dispenses with the need for heating, and with the possibility of adverse smell associated with solvent use. The current solvent-less process involves dissolving photochromic compounds in melted polymer or resin materials, and coating the transient document with the melted composition. In embodiments, the photochromic compounds are spiropyrans.